1. Technical Field
The present invention relates to an image reading device that reads an image of an object by guiding light from a light source via a light guiding member and irradiating the object with the light, and by detecting the light from the object.
2. Related Art
In image scanners, facsimiles, copy machines, banking terminal devices, or the like, a contact image sensor module (hereinafter, abbreviated as “CIS module”) is used as an image reading device. This CIS module reads an image of an object to be read by irradiating the object to be read with light, and detecting the reflected light at this time with an optical sensor. In addition, an imaging optical system having an imaging magnification of an erect equal-magnification is generally used to appropriately guide the reflected light from the object to be read to the optical sensor. That is, this imaging optical system images the light reflected by the object to be read at an erect equal-magnification, and images the erect equal-magnification image of the object to be read toward the optical sensor. Then, the optical sensor is able to read the image of the object to be read by detecting the erect equal-magnification image imaged by the imaging optical system.
However, JP-A-2000-066134 discloses an imaging optical system that changes the direction of the optical axis (that folds the optical axis) by reflecting light using a roof prism, to achieve miniaturization of the CIS module. In this imaging optical system, an object-side lens is disposed to be opposite the object to be read, and an image-side lens that links the image of the object to be read to an image plane in cooperation with the object-side lens are provided. In addition, a roof prism is disposed in the light path from the object-side lens to the image-side lens. Therefore, the light, which is reflected by the object to be read and is transmitted through the object-side lens, is reflected by the roof prism lens and the propagation direction thereof is changed and is made to face toward the image-side lens. In this way, miniaturization of the CIS module may be achieved by using a reflection plane (roof prism) to change the propagation direction of the light.
However, the image reading device needs an illumination unit that irradiates an object with light. In JP-A-2000-066134, an illumination light source is provided as this illumination unit. However, in addition to the illumination light source disclosed in JP-A-2000-066134, to appropriately irradiate the object with light generated at the light source, it is also preferable to include a light guide that guides the light generated at the light source and irradiates the object with this light. However, when such a light guide is separately provided in addition to the light source, miniaturization of the image reading device may become difficult.
In addition, miniaturization of the image reading device may be difficult for the following reasons. That is, in the image reading device provided with the above-described optical sensor and the light source, it is necessary to provide substrates on which the optical sensor and the light source are mounted. However, when the substrate is provided with respect to each of the optical sensor and the light source, it may also be difficult to miniaturize the image reading device.